This invention relates to a high pressure fuel injection device for an engine and more particularly to an improved high pressure fuel injection device that controls the amount of fuel injected to the engine in response to all running conditions of the engine.
There is a known and popular type of fuel injection system that includes an injector nozzle of the type called the "accumulator type". This type of injection nozzle includes an accumulator chamber that has a nozzle port that is adapted to communicate the accumulator chamber with the combustion chamber of the engine. An injection valve controls the opening and closing of the nozzle port and is operated by means of an actuator device that is supported within a control chamber. Fuel is delivered under pressure to both the accumulator chamber and that control chamber and when both chambers are at the same pressure, the injection valve will be held in its closed position. In order to permit the injection of fuel, a relief valve that controls the pressure in the control chamber is open so as to permit the pressure in the control chamber to be relieved. When this happens, the fuel pressure in the accumulator chamber causes opening of the injection valve and fuel is injected into the engine.
This type of system is extremely effective and is very popular. However, the relief valve is normally operated by means of an electromagnet and the timing of the opening of the relief valve and the duration of its opening is related to the crankshaft or engine output shaft angle of the engine. Normally, the valve is held open for a fixed duration of the angular rotation of the crankshaft. As a result, when the engine is turning at a higher engine speed, the actual opening time of the relief valve and accordingly the discharge time of the nozzle will be less than when operating at low speeds. As a result, if the fuel delivery is designed so as to be adequate at high speed, the engine will tend to run over rich at low speeds. Alternatively, if the engine is operated at the desirable fuel/air mixture at low engine speeds, it will tend to run lean at high engine speeds.
It is, therefore, a principal object of this invention to provide an improved fuel injection system embodying an accumulator type fuel injection nozzle.
It is a further object of this invention to provide an improved accumulator type nozzle fuel injection system wherein the amount of fuel discharged under all running conditions may be maintained at the desirable amount.
It is a further object of this invention to provide an extremely simple and yet effective method for controlling the amount of fuel discharged by an accumulator type injection nozzle under all running conditions.